[5.10, 5.15] New bpf kselftest failure

Luiz Capitulino
2023-07-17T13:04:46Z

Hi,

The upstream commit below is backported to 5.10.186, 5.15.120 and 6.1.36:

"""
commit ecdf985d7615356b78241fdb159c091830ed0380
Author: Eduard Zingerman <eddyz87@gmail.com>
Date: Wed Feb 15 01:20:27 2023 +0200

bpf: track immediate values written to stack by BPF_ST instruction
"""

This commit is causing the following bpf:test_verifier kselftest to fail:

"""
# #760/p precise: ST insn causing spi > allocated_stack FAIL
"""

Since this test didn't fail before ecdf985d76 backport, the question is
if this is a test bug or if this commit introduced a regression.

I haven't checked if this failure is present in latest Linus tree because
I was unable to build & run the bpf kselftests in an older distro.

Also, there some important details about running the bpf kselftests
in 5.10 and 5.15:

* On 5.10, bpf kselftest build is broken. The following upstream
commit needs to be cherry-picked for it to build & run:

"""
commit 4237e9f4a96228ccc8a7abe5e4b30834323cd353
Author: Gilad Reti <gilad.reti@gmail.com>
Date: Wed Jan 13 07:38:08 2021 +0200

selftests/bpf: Add verifier test for PTR_TO_MEM spill
"""

* On 5.15.120 there's one additional test that's failing, but I didn't
debug this one:

"""
#150/p calls: trigger reg2btf_ids[reg→type] for reg→type > __BPF_REG_TYPE_MAX FAIL
FAIL
"""

* On 5.11 onwards, building and running bpf tests is disabled by
default by commit 7a6eb7c34a78498742b5f82543b7a68c1c443329, so I wonder
if we want to backport this to 5.10 as well?

Thanks!

- Luiz